The Project Period tor Year 1 of the K99 Award ended March 1. 2009. I am currently in Year i or the K99 Award. Since only a short time has passed since the last report, 1 am only providing a brief update in addition to the Progress Report for Year 1. In the previous report, I described preliminary data from the first set of inten/ention studies In the rat NEC model. To increase the number of animals per group and to be able to calculate significances, we repeated the'intervention study with more anlmials. The figure below shows that rats receiving formula without HMO developed NEC with an average pathology score of 1.98[unreadable]0.34. The pathology score was significantly reduced to 0.79[unreadable]0.39. 0.64[unreadable]0.54 and 0.44[unreadable]0.30 when the formula was supplemented with HMO at 0.1, 1, and 10 mg/mL, respectively. The range of 0.1 and 10 mg/mL resembles the HMO concentration in rat and human milk, respectively. None of the rats that received HMO had a pathology score that was higher than the average score of rats that received formula without HMO. Breast-fed pups had an average score of only 0.15[unreadable]0.34, which was not significantly different from rats that received HMO with their formula. This is the first in vivo data showing that HMO significantly reduce NEC In an animal disease model. This data confirms our initial hypothesis and justifies all future experiments originally proposed for the ROO phase of the award. In the beginning of the ROO phase, we will continue with the experiments proposed in Specific Aim 1 and analyze whether HMO alter mucosal neutrophil infiltration and activation and whether HMO alter the intestinal barrier function. Afterwards, we will move on to Specific Aim 2, 3 and 4.